In the initial stages of the production of cut filler for smoking articles such as cigarettes, cured tobacco leaf is classified into top, middle and bottom leaf, the top leaves being those nearest the plant top, or mixtures thereof. These classes are further graded by quality and the resulting numerous grades of leaf are threshed to remove the leaf lamina from the stem or mid rib, and are redried and packed for shipment. Between curing and redrying, the leaf and stem are usually referred to as xe2x80x9cgreenxe2x80x9d.
In conventional processes, the stem grades are classified by diameter and length, dried to an o.v. (oven volatiles content) of around 10 or 11% and classified into long stem pieces suitable for direct use, subject to primary processing in filler, and shorter stem pieces suitable for use in the manufacture of tobacco sheet. The stem is packaged for transport from the stemmery to the cigarette factory, which may well be in another country or continent. In the cigarette factory, the long stems for direct use as filler are preblended with other stems from the same and/or different sources, and subjected to primary processing including conditioning and soaking in water for a few hours followed by rolling flat, cutting and drying using known techniques. The cut dried stem is blended with cut tobacco lamina which has been subjected to a primary processing to provide a cut filler for cigarettes or other smoking articles.
In conventional processes, the stems are subjected to mechanical damage during rolling, because their structure has been weakened by the drying process and subsequent insufficient conditioning because of insufficient moisture penetration. The rolled stems are of different thicknesses because the stems prior to rolling are of different diameters, lengths and physical properties. This means that the final cut stem filler for blending with cut lamina filler are not of optimal quality.
According to the invention there is provided a process for preparing tobacco stem for use as filler for a smoking article comprising:
classifying the tobacco stem to provide a plurality of stem grades;
rolling each stem grade separately, each grade being rolled under rolling conditions optimised for that grade. It is preferred that the rolling conditions for each grade are such that the resulting rolled stems of all grades are of a substantially uniform thickness. It is also preferred that the classification is according to the position on the tobacco plant of the leaf from which the stem originated.
Alternatively, the classification is according to stem diameter. Most preferably, the classification is according to the position on the tobacco plant of the leaf from which the stem originated and then by further classifying each resulting grade of stem prior to rolling according to stem diameter to produce the plurality of grades for rolling. Also preferably, the classification according to the position on the tobacco plant of the leaf from which the stem originated is conducted on cured tobacco leaves prior to threshing.
It is also preferred that a further classification is carried out on the green flat rolled stems, preferably before drying; this classification (cleaning) may be by air separation, and can produce a grade of rolled stem suitable for direct use for primary processing into filler without drying, and a by-product suitable for the manufacture of tobacco sheet. After drying, a further stem classification, similar to the previously described classification, can be conducted on the dried rolled stem.
All the processing steps mentioned above (other than primary processing and manufacture of tobacco sheet) can be carried out in the stemmery prior to packaging of the rolled stem and shipping to the cigarette factory The rolled stem may be dried prior to packaging for transport, before or after any post rolling classification.
The invention also provides, in a second aspect, a process for preparing tobacco stem for use as filler for a smoking article comprising grading rolled tobacco stem into at least two grades.
The invention also provides a process for the manufacture of smoking articles such as cigarettes comprising forming cut filler made by a process according to the first or second aspects of the invention into a smoking article.
The invention also provides a smoking article comprising filler made by a process according to the first or second aspects of the invention.